The present invention relates to the art of polishing a workpiece with a polishing tape.
1. Background Art
Japanese Patent Document. TOKU-KAI-HEI 8-257899 discloses an example of the art of polishing a workpiece with a polishing tape. This prior art realates to the art of polishing a workpiece, by rotating the workpiece while pressing a press member against a back surface of a polishing tape and thereby pressing the polishing tape against the workpiece.
In the prior art, xe2x80x9can axis line about which a workpiece is rotatedxe2x80x9d may, or may not, coincide with an axis line of a target portion of the workpiece that is to be polished. For example, in the case where a camshaft of an engine is a workpiece and a cam surface of a cam portion of the camshaft is a target surface of the target portion that is to be polished, xe2x80x9can axis line of rotation of the workpiecexe2x80x9d coincides with an axis line of the target portion. However, in the case where a crankshaft of an engine is a workpiece and an outer surface of a pin-like portion as a connection portion of the crankshaft that is to be connected to a connecting rod is a target surface, xe2x80x9can axis line of rotation of the workpiecexe2x80x9d does not coincide with an axis line of the target portion.
2. Disclosure of Invention
In the prior art, the press member is movable along a straight line which crosses the rotation axis line of the workpiece. However, in the prior art, the press member cannot do any other sort of motion. Therefore, in the case where an angle defined by the target surface and the rotation axis line of the workpiece changes in a direction in which the target surface continues, the press member cannot follow the workpiece. Thus, the shape of the workpiece the press member can follow is limited.
The present invention has been developed in the above-indicated background, and an object thereof is to improve the ability of a press member to follow a workpiece.
The above-indicated object is achieved according to each of the following features of the present invention. These features are given respective sequential numbers and are described in the same manner as that in which claims are described, i.e., any feature that includes another feature shall do so by referring to the number given to the latter feature. This is for helping more easily understand that two or more of the following features may be combined.
(1) An apparatus for polishing a workpiece, by rotating the workpiece while pressing a press member against a back surface of a polishing tape and thereby pressing the polishing tape against the workpiece, the apparatus being characterized in that the apparatus includes a holding portion which holds the press member, and the holding portion includes a rollable-type holding device which holds the press member such that the press member is rollable about a rolling axis line which crosses a rotation axis line about which the workpiece is rotated.
In this apparatus, the press member is rollable about a rolling axis line which crosses the rotation axis line of the workpiece. Therefore, in this apparatus, the press member can follow the workpiece not only in the case where the angle defined by the target surface and the rotation axis line of the workpiece does not change in the direction in which the target surface continues but also in the case where the angle changes.
In addition, in this apparatus, the press member is made rollable relative to the rotation axis line of the workpiece, because the press member is made rollable relative to the holding portion of the apparatus. Therefore, as compared with the case where both the press member and the holding portion are made rollable relative to the rotation axis line of the workpiece, inertia which resists the rolling of the press member can be decreased, which also contributes to improving the ability of the press member to follow the workpiece.
In this apparatus, xe2x80x9cthe rotation axis line about which the workpiece is rotatedxe2x80x9d may or may not, coincide with an axis line of the above-indicated target portion.
In addition, the phrase of xe2x80x9ca rolling axis line which crosses a rotation axis line about which the workpiece is rotatedxe2x80x9d means not only the case where the rolling axis line intersects the rotation axis line but also the case where the rolling axis line does not intersect the rotation axis line, i.e., crosses over the rotation axis line in a three-dimensional space.
(2) An apparatus according to the feature (1), wherein the rolling axis line is substantially parallel to a straight line which contacts a contact surface of the press member that contacts the workpiece, at a position corresponding to a contact position where the polishing tape contacts the workpiece, and which perpendicularly crosses over the rotation axis line of the workpiece in a three-dimensional space.
(3) An apparatus according to the feature (1) or (2), wherein the rolling axis line is located it a position about which, during the polishing of the workpiece, a moment which rolls the press member to follow the workpiece is produced by a force which is exerted by the workpiece to the press member.
This apparatus does not essentially need a device which produces a force to roll the press member, and exerts the force to the press member so that the press member can follow the workpiece. Thus, the ability of the press member to follow the workpiece can be improved w*without complicating the construction of the polishing apparatus.
(4) An apparatus according to any one of the features (1) to (3), wherein the rolling axis line substantially coincides with a straight line which contacts a contact surface of the press member that contacts the workpiece, at a position corresponding to a contact position where the polishing tape contacts the workpiece, arid which crosses over the rotation axis line of the workpiece in a three-dimensional space.
In this apparatus, the contact surface of the press member that contacts the polishing tape can change its inclination relative to the rotation axis line of the workpiece, without changing its position relative to the same. Therefore, in this apparatus, a width of the contact surface (i.e., a dimension of the surface in a direction parallel to the rotation axis line of the workpiece) need not be much longer than that of the target surface (i.e., a dimension of the surface along the rotation axis line of the workpiece). Thus, the size and weight of the press member can be decreased, and the inertia of the same can also be decreased, both of which contribute to improving further the ability of the press member to follow the workpiece.
(5) An apparatus according to the feature (4), wherein the contact surface of the press member is one which straightly extends, like a belt, along the polishing tape, and the rolling axis line coincides with a center line of the contact surface that extends in a direction in which the polishing tape extends.
(6) An apparatus according to any one of the features (1) to (5), further including a pair of tape-support, portions which contact and support the polishing tape, at two positions between which the press member is located, and are moved with the press member.
In this apparatus, since the pair of tape-support portions follow the press member, the polishing tape is bent at a stable angle by the press member, though the press member is moved relative to the holding portion.
(7) An apparatus according to the feature (6), wherein the pair of tape-support portions include a pair of guide rollers each of which is freely rotatable.
(8) An apparatus according to the feature (6), wherein the pair of tape-support portions include a pair of stationary contact portions each of which is fixed in position.
(9) An apparatus according to any one of the features (1) to (8), wherein the contact surface of the press member that contacts the polishing tape is curved toward the workpiece as viewed in a lengthwise direction of a polishing tape.
(10) An apparatus according to any one of the features (1) to (9), wherein the press member is held by the holding portion via a cartridge which is detachably attached to the holding portion, and the rollable-type holding device holds, on the cartridge, the press member such that the press member is rollable relative to the cartridge.
It is desirable that the rollable-type holding device according to the feature (1) be easily maintained. In the polishing apparatus according to this feature, the cartridge including the rollable-type holding device can be easily separated from the holding portion of the apparatus. Thus, the ease of maintenance of the rollable-type holding device is improved.
(11) An apparatus according to any one of the features (1) to (10), further including a movable-type holding device which holds the press member such that the press member is movable relative to the holding portion along a movement axis line which crosses the rotation axis line of the workpiece.
In the case where the rotation axis line of the workpiece does not coincide with the axis line of the target portion, or in the case where the rotation axis line of the workpiece coincides with the axis line of the target portion but the target surface is a non-cylindrical surface such as a cam surface of a camshaft of an engine, a distance between a position where the press member presses the polishing tape against the target surface, and the rotation axis line of the workpiece changes in the direction in which the target surface continues. In the polishing apparatus according to the feature (11), the press member is movable in a direction which crosses the rotation axis line of the workpiece. Therefore, in this apparatus, if the above-indicated distance changes in the direction of continuation of the target surface, the press member is moved relative to the rotation axis line of the workpiece, and relative to a base portion of the apparatus. Thus, the ability of the press member to follow the workpiece can be improved, while at the same time the inertia to resist the movement of the press member can be reduced.
The phrase xe2x80x9cthe rotation axis line about which the workpiece is rotatedxe2x80x9d, and the phrase of xe2x80x9ca rolling axis line which crosses a rotation axis line about which the workpiece is rotatedxe2x80x9d can be construed to have the same meanings as those described in connection with the feature (1).
(12) An apparatus according to the feature (11), wherein the movable-type holding device includes a rotation preventing mechanism which prevents the press member from rotating about an axis line which crosses the rolling axis line.
(13) An apparatus according to title feature (11) or (12), further including a biasing device which biases the press member toward the workpiece.
In this apparatus, xe2x80x9cthe biasing devicexe2x80x9d may be of a type which utilizes an elastic force of an elastic member as a biasing force; of a type which utilizes a pressure as a biasing force; or of a type which utilizes a magnetic force as a biasing force.
(14) An apparatus according to any one of the features (11) to (13), wherein the press member is held by the holding portion via a cartridge which is detachably attached to the holding portion, and the movable-type holding device holds, on the cartridge, the press member such that the press member is movable relative to the cartridge.
It is desirable that like the rollable-type holding device according to the feature (1), the movable-type holding device according to the feature (11) be easily maintained. In the polishing apparatus according to this feature, the cartridge including the movable-type holding device can be easily separated from the holding portion of the apparatus. Thus, the ease of maintenance of the movable-type holding device is improved.
(15) An apparatus according to any one of the features (1) to (14), including
a workpiece rotating device which rotates the workpiece about the rotation axis line, and
a tape holding device which holds the polishing tape and which includes (a) the holding portion, (b) a cartridge which is detachably attached to the holding portion and which holds the polishing tape at a position opposed to the target surface of the workpiece, and (c) the press member which is held by the cartridge and which presses the back surface of the polishing tape and thereby presses the polishing tape against, the target surface of the workpiece.
(16) A method of polishing a workpiece, by rotating the workpiece while pressing a press member against a back surface of a polishing tape and thereby pressing the polishing tape against a target surface of the workpiece, the method being characterized in that during the polishing of the workpiece the press member is rolled about a rolling axis line which crosses the rotation axis line of the workpiece, so that the press member follows the workpiece.
In this method, the press member can follow the workpiece even in the case where the angle defined by the target surface and the rotation axis line of the workpiece changes in the direction in which the target surface continues.
(17) A method according to the feature (17), wherein the press member is rolled about the rolling axis line relative to a holding portion which holds the press member.
In this method, the inertia to resist the rolling of the press member can be reduced, which leads to improving the ability of the press member to follow the workpiece.